When Kit Harington — sporting a loincloth and knee-high sandals — strides into a crumbling arena for his first scene in the action flick “Pompeii,” in theaters Friday, you might just be reminded of “Gladiator,” which made Russell Crowe a huge star back in 2000. Only, let’s be honest, Crowe never had Harington’s long, curly locks.

The hair. The brooding intensity. The chiseled body. It’s all already earned Harington legions of fans from his turn as Jon Snow on “Game of Thrones,” the hit HBO show based on the books by George R.R. Martin. But, true to that introverted character, the actor blushes at all the attention.

“It really does feel like being a rock star. You have crying fans who are trying to touch you and things,” Harington tells The Post. “I get a little bit embarrassed by it, really. I’m quite shy at heart.”

Besides, the 27-year-old says, “When I was at drama school, I was always playing the innocent, young, baby-faced ones. Now I’m playing this action-figure type, and they sort of fall under the sex symbol category.”

He quickly adds: “I never really see myself as that, otherwise I think I’d have an ego problem.”

The modest actor, whose full name is Christopher Catesby Harington, was born in Worcester, England, to not-so-humble beginnings.

His great-grandfather was Sir Richard Harington, the 12th Baronet Harington. The actor’s father is an artist and his mother, a playwright, would often take the family to see productions at the Royal Shakespeare Company.

Harington, who says his interest in acting came from those early trips to the theater, attended London’s Central School of Speech and Drama. Nick Moseley, one of his acting teachers, remembers him as self-assured, with “the manners of a true gentleman.

“Kit was unusual in that even before he became a well-known actor, he always had an inner confidence which was the opposite of arrogance,” Moseley says. “I think then I put it down to his aristocratic roots!”

After graduating in 2008, Harington landed a major role as Albert in the Royal National Theatre’s critically acclaimed “War Horse.”

His schoolmate Toby Olié joined the production of “War Horse” at the same time, as one of the three puppeteers maneuvering the giant horse that Harington rode onstage.

“I remember him walking around with those [George R. R. Martin] books in his hands,” Olié says. “He had this audition coming up. Now, [the show] is huge over in England. It’s still quite surreal. I literally carried that guy onstage for a year!”

In the HBO fantasy series — which returns April 6 — Harington plays Jon Snow, the bastard son of the Stark family, who takes a vow of celibacy to defend his territory.

Last season, Snow finally got some action, when he lost his virginity to brazen wildling Ygritte (played by Rose Leslie).

That love scene may have been an easy one for Harington, who was rumored to be dating Leslie. (They reportedly split in August.) Though the actor has never commented on the relationship and won’t confirm whether or not he’s currently single, he will talk about the qualities he seeks in a partner. “I go for the tough smartass,” he says. “I like a girl who takes the piss out of me.”

Intertwined with plenty of fight and disaster scenes in “Pompeii” is the sweet love story between Harington’s Milo, a slave-turned-gladiator, and Emily Browning’s Cassia, the daughter of a wealthy merchant. Harington says he spent quality time getting to know his co-star before filming began.

“We just got on really well from the get-go,” Harington says. “We kind of took the piss out of each other. It built a really good rapport with us — so much so that when it came to kissing her, it felt really strange.”